Currently, ABO serum grouping performed by gel technology employs a red cell diluent containing EDTA (MTS Diluent 2 Plus) that does not permit extended storage of the red cell suspensions. A diluent currently used for suspension and long-term storage of reagent red cells for antibody detection and identification (Ortho 0.8% Red Cell Diluent) was evaluated for use with A(1) and B cells. Because this diluent does not contain EDTA, testing was limited to EDTA samples. As a comparison, a Micro Typing Systems (MTS) diluent not containing EDTA (MTS Diluent 2) was also tested. MTS-suspended red cells were maintained for 24 hours and compared with Ortho-Clinical Diagnostics 0.8% suspended red cells maintained for 7 days. ABO serum grouping was performed on 144 EDTA plasma samples using all three cell suspensions. Acceptable results were noted in all aspects of testing.